While the containers are really useful, the user experience is lacking.
For example the sort button has no confirmation. I clicked by mistake and all my tabs are now sorted by some weird logic and not by my context. And I cannot revert this.

If I remove a page to open in certain container, after syncing it will come back and page will still open in that container. But I deleted page from the container.

This is the closest I've found to Chrome's tab system (super helpful for students) but I wish you were able to edit/add more categories.

Классный виджет.
Пользуюсь давно.
Косяков нЕ обнаружено за всё время))

This is Firefox's killer app